It is well known that several sheets of glass may be mounted on means holding them in a spaced relationship to provide an insulated window pane. Representative structures of this kind are illustrated in the U.S. Pat. No. to Geyer, 1,975,895, Oct. 9, 1934 and Eisenberg, U.S. Pat. No. 3,553,913, Jan. 12, 1971. In the usual thermal pane construction, a rectangular frame constituting a spacer means is coated on its sides with a sealant and the sheets of glass are cemented to the spacer means sandwiched between the glass sheets to produce a thermal pane having dead air space between the sheets. A dessicant is usually carried in the spacer device to eliminate the condensation of any moisture on the glass, which moisture might have been trapped within the enclosed chamber.
To effect the assembly of such thermal panes, it has been the usual practice to provide aluminum channel spacer elements that are as long as each peripheral side of the glass sheets to be assembled and then weld the spacer elements together to form a rectangular spacer frame or by making use of corner key elements that have right angular shapes, as shown in Lacombe, U.S. Pat. No. 4,080,482, Mar. 21, 1978.
After the rectangular frame is put together, a sealant may be applied to the sides of the frame, requiring several manipulative steps to properly coat both walls of each side of the rectangular frames. While applying the sealant during this coating process, it is possible that the sealant will not be applied uniformly due to the necessity for shifting the square frame after each side is coated and also it is possible that foreign matter may contact the applied sealant as the frame is turned from side to side to complete the four-sided coating operation. Should any fingerprints or any foreign matter come in contact with the more or less sticky, hot melt sealant during these manipulations or if an uneven coating layer is applied to one or more of the respective walls of the four-sided frame caused by the shifting of the frame relative to the applicator, a proper seal could not be made and the resulting thermal pane will be defective.